Class-D driving method for stereo load

ABSTRACT

The present invention provides a class D amplifier and method for driving a tri-wired stereo amplifier. Additionally, the class D amplifier includes a first filter, a second filter, a processor, a 2D-quantitizer, a signal generator, and a logic circuit. The class D amplifier and method of the invention can reduce cost of production and increase processing efficiency. More particularly, the class D amplifier and method of the invention are processed in an optimal feedback mode, so as to reduce the reciprocal effect between the two channels, and avoid mismatch of the two amplifiers.

FIELD OF THE INVENTION

The present invention relates to a Class D amplifier and its method,more specifically, it relates to a Class D amplifier based on athree-phase full-bridge structure and its method of driving Tri-wiredstereo amplifier.

BACKGROUND OF THE INVENTION

Audio amplifier has wide-spread application in all electronic productsthat need audio output, for example, walkman, audio set, MP3 player, PDAand cellular phone, etc. The conventional Audio amplifier can becategorized as A type, B type, AB type and D type, etc. Among them, Atype, B type and AB type amplifier are the so-called linear amplifierand class D amplifier is nonlinear amplifier called pulse widthmodulation (PWM) amplifier.

A type amplifier usually just has one active component, for example,transistor. The transistor needs a bias circuit, therefore, no matterhow large the input signal is, it can not be in fully conducted or fullynon-conducted state and this conducted/non-conducted region is theso-called linear region. A type amplifier has the advantage of highlinearity in its response and thus low loss of fidelity in its output,which makes it suitable for high fidelity audio system. However, A typeamplifier has very low efficiency with a theoretical power efficiency ofabout 25% but an actual power efficiency of only about 15% to 20%.Additionally, A type amplifier will generate large amount of heat duringthe use at large power, it is thus not suitable to be used as portableequipment.

B type amplifier is generally composed of two transistors pushing eachother, one outputs the current and the other absorbs the current and theeffect of amplification is achieved through alternate conduction ofthese two transistors. B type amplifier has larger power efficiency thanthat of A type amplifier, that is, it has a theoretical power efficiencyof about 78% and the real power efficiency is in between 50% to 70%.However, when the input signal is smaller than the conduction voltage ofthe transistor, both transistors will be at non-conducted states, thisis the so-called intermodulation distortion. Therefore, B type amplifieris not linear in the whole dynamic range.

Additionally, AB type amplifier is a combination of A type and B typeamplifier. Its structure is very similar to B type amplifier but acircuit which can provide small bias current to each transistor isadopted; therefore, each transistor will not be in fully non-conductedstate. Its power consumption is larger but the intermodulationdistortion can be almost eliminated. Its operation is similar to B typeamplifier and two transistors are associated to complete the mission,however, the overall performance is a little bit better than that of Btype amplifier. The theoretical power efficiency of AB type amplifier isabout 78% but the actual value is in between 50% to 70%.

The common disadvantages of the above mentioned A type, B type and ABtype amplifier are the needs of good heat-dissipating equipment andspace. Therefore, they are mostly bulky and the operation consumes a lotof power. Under the trend of low power consumption, small form factorand light weight pursued by most electronic products, those linearamplifiers thus are not suitable to be used in such electronic products.

Therefore, CLASS D AMPLIFIER is thus developed with an efficiency higherthan the above mentioned linear amplifier (class D amplifier has atheoretical power efficiency of about 100% but the actual powerefficiency is still higher than 85%) to meet the above mentioned needs.Class D amplifier can save more power and improve the lifetime ofbattery due to its high power efficiency. Moreover, class D amplifiergenerates lower heat during its operation and thus can reduce the energycontrol cost. What's even more is some class D amplifiers do not needheat-dissipating devices and thus the volume of equipment which adoptsthat kind of amplifier can be much smaller.

Currently, lots of literature discloses several improved class Damplifiers in an attempt to further increase the power efficiency andenhance the stability of class D amplifier; moreover, its circuit isfurther simplified and its volume is even smaller and the fidelity lossis even fewer. For example, U.S. Pat. No. 4,689,819 discloses how tomake the CMOS device of class D amplifier more efficient under smallervolume and compatible battery set; U.S. Pat. No. 5,317,640 discloses howclass D amplifier can reduce the current and reduce in turn the powerconsumption when the input signal is zero, this makes it suitable to beused in the driving of mono channel or hearing aids; U.S. Pat. No.6,016,075 discloses a class D amplifier which can reduce cost and DCcomponent error; U.S. Pat. No. 6,924,700 discloses a class D amplifierwith correction circuit; U.S. Pat. No. 7,078,964 discloses class Damplifier having DC current detection circuit.

However, in the prior art, when class D amplifier is used to drive dualchannel tri-wired stereo amplifier, half-bridge circuit architectureneeds to be used to realize this idea; since this method needs thesupply of bipolar power for its operation, it is thus not suitable to beused in portable products. If it is to be used in portable product anduni-polar power, such as battery, is used as the power supply, then agenerator circuit of half voltage point is needed to drive theamplifier; since the half voltage point generator circuit is analogcircuit, temperature drift, input voltage drift and process drift mustbe considered during the designing stage, the output voltage is thuseasily changed by different working environments, which might furtherlead to power consumption due to the need of extra circuit and mightaffect the audio output quality of the entire system.

SUMMARY OF THE INVENTION

Therefore, one of the application scope of the current invention is toprovide a class D amplifier and a method for driving a tri-wired stereoamplifier. According to the class D amplifier of the present inventionand its driving method, it can eliminate the use of prior arthalf-bridge circuit architecture and thus reduce the production cost andenhance the efficiency. More specifically, class D amplifier of thepresent invention and its driving method is performed under optimalfeedback method which can reduce the mutual influence of two audiochannels and avoid the mismatches between two speakers.

A preferred embodiment of the present invention of class D amplifier isused to drive a tri-wired stereo amplifier. The class D amplifiercontains a first filter, a second filter, a processor, a two dimensionalquantitizer, a signal generator and a logic circuit.

Furthermore, the first filter receives a first left audio channel soundsignal and a first right audio channel sound signal from a soundgenerator unit; moreover, with the use of a over-sampling frequency, thefirst left audio channel sound signal is processed to a second leftaudio channel sound signal and the first right audio channel soundsignal is processed to a second right audio channel sound signal.

The second filter is coupled to the first filter and the two dimensionalquantitizer so as to receive the second left audio channel sound signaland the second right audio channel sound signal from the first filterand to receive a first left audio channel triggering signal and a firstright audio channel triggering signal from the two dimensionalquantitizer. Moreover, the second filter re-configures the second audiochannel sound signal and the first triggering signal according to afrequency weighted average function so as to generate a left audiochannel error signal corresponded to the second left audio channel soundsignal and the first left audio channel triggering signal; and,moreover, a right audio channel error signal corresponded to the secondright audio channel sound signal and the first right audio channeltriggering signal.

Moreover, the processor is coupled to the second filter so as to receivethe left audio channel error signal and the right audio channel errorsignal. And the error signal is used to calculate a left audio channeloptimal signal corresponded to the left audio channel error signal and aright audio channel optimal signal corresponded to the right audiochannel error signal.

The two dimensional quantitizer is coupled to the processor in order toreceive the left audio channel optimal signal and the right audiochannel optimal signal, and to convert those optimal signals into asecond left audio channel triggering signal corresponded to the leftaudio channel optimal signal and a second right audio channel triggeringsignal corresponded to the right audio channel optimal signal.Furthermore, the two dimensional quantitizer sends the second left audiochannel triggering signal and the second right audio channel triggeringsignal to the second filter to replace respectively the first left audiochannel triggering signal and the first right audio channel triggeringsignal.

Moreover, the signal generator is coupled to the two dimensionalquantitizer in order to receive the second left audio channel triggeringsignal and the second right audio channel triggering signal; in the meantime, multiple driving signals are generated according to the secondtriggering signal.

The logic circuit contains multiple switches wherein each switchcorresponds to each of the multiple driving signals. Furthermore, thelogic circuit is coupled to the signal generator in order to receive themultiple driving signals and the multiple driving signals are used tocontrol the corresponding switch in the logic circuit and to furtherdrive the tri-wired stereo amplifier.

A method for driving a tri-wired stereo amplifier according to apreferred embodiment of the present invention comprising the followingsteps:

(a) Receiving a first left audio channel sound signal and a first rightaudio channel sound signal.

(b) Associating an over-sampling frequency to process the first leftaudio channel sound signal to a second left audio channel sound signal;and furthermore, processing the first right audio channel sound signalto a second right audio channel sound signal.

(c) Re-configuring the second audio channel sound signal, a first leftaudio channel triggering signal and a first right audio channeltriggering signal according to a frequency weighted average function inorder to generate a left audio channel error signal corresponded to thesecond left audio channel sound signal and the first left audio channeltriggering signal and to generate a right audio channel error channelcorresponded to the second right audio channel sound signal and thefirst right audio channel triggering signal.

(d) Calculating a left audio channel optimal signal corresponded to theleft audio channel error signal and a right audio channel optimal signalcorresponded to the right audio channel error signal.

(e) Converting those optimal signals into a second left audio channeltriggering signal corresponded to the left audio channel optimal signaland a second right audio channel triggering signal corresponded to theright audio channel optimal signal.

(f) Using respectively the second left audio channel triggering signaland the second right audio channel triggering signal to replace thefirst left audio channel triggering signal and the first right audiochannel triggering signal.

(g) Generating multiple driving signals according to those secondtriggering signals.

(h) Using those multiple driving signals to control the correspondingmultiple switches in a logic circuit so as to drive the tri-wired stereoamplifier.

The advantages and spirit of the present invention can be furtherunderstood through the following detailed descriptions and the figuresattached.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the functional block diagram of a class D amplifierof a preferred embodiment of the present invention.

FIG. 2 illustrates a logic circuit of an embodiment of the presentinvention.

FIG. 3A illustrates the output input relationship chart of twodimensional quantitizer generated when those second triggering signalsof the present invention are limited to five values of 0, 1, −1, ½, −½.

FIG. 3B illustrates the output input relationship chart of twodimensional quantitizer generated when those second triggering signalsof the present invention are limited to three values of 0, 1 and −1.

FIG. 4 illustrates the electronic circuit block diagram of twodimensional quantitizer of one embodiment of the present invention andwe can see that it can realize the triggering signal set of FIG. 3B.

FIG. 5 illustrates the block diagram of a method for driving tri-wiredstereo amplifier for a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a class D amplifier for driving atri-wired stereo amplifier and its driving method. In the followings,some embodiments and real application cases of the present inventionwill be described in details in order to fully explain the features,spirit and advantages of the present invention.

Please refer to FIG. 1 which shows the functional block diagram of oneembodiment class D amplifier of the present invention. As shown in FIG.1, the class D amplifier 1 contains a first filter 10, a second filter12, a processor 14, a two dimensional quantitizer 16, a signal generator18 and a logic circuit 19. Moreover, the class D amplifier 1 can be usedto drive a tri-wired stereo amplifier 30.

The first filter 10 receives a first left audio channel sound signal(AS_(L)) and a first right audio channel sound signal (AS_(R)) from asound generator unit (not drawn in the figure). Meanwhile, the firstfilter 10, associated with an over-sampling frequency, can process thefirst left audio channel sound signal (AS_(L)) to a second left audiochannel sound signal (AS_(L)′) and process the first right audio channelsound signal (AS_(R)) to a second right audio channel sound signal(AS_(R)′).

The second filter 12 is coupled to the first filter 10 and the twodimensional quantitizer 16 so as to receive the second left audiochannel sound signal (AS_(L)′) and the second right audio channel soundsignal (AS_(R)′) from the first filter 10 and to receive a first leftaudio channel triggering signal (T_(L1)) and a first right audio channeltriggering signal (T_(R1)) from the two dimensional quantitizer 16.Furthermore, second filter 12 re-configure those second audio channelsound signals (AS_(L)′, AS_(R)′) and those first triggering signals(T_(L1), T_(R1)) according to a frequency weighting function so as togenerate a left audio channel error signal (E_(L)) corresponded to thesecond left audio channel sound signal (AS_(L)′) and the first leftaudio channel triggering signal (T_(L1)) and a right audio channel errorsignal (E_(R)) corresponded to the second right audio channel soundsignal (AS_(R)′) and the first right audio channel triggering signal(T_(R1)).

In the real application, the frequency weighting function matches thefollowing [Equation 1]:

$\begin{matrix}\left\{ \begin{matrix}{\begin{bmatrix}{X_{R}\left( {k + 1} \right)} \\{X_{L}\left( {k + 1} \right)}\end{bmatrix} = {{A\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {B\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}} \\{\begin{bmatrix}{E_{R}(k)} \\{E_{L}(k)}\end{bmatrix} = {{C\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {D\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}}\end{matrix} \right. & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

wherein,

$\begin{bmatrix}X_{R} \\X_{L}\end{bmatrix} \in R^{n \times 1}$

is the status of class D amplifier;

AεR^(n×n); BεR^(n×2); CεR^(2×n); and DεR^(2×2).

Furthermore, the processor 14 is coupled to the second filter 12 so asto receive the left audio channel error signal (E_(L)) and the rightaudio channel error signal (E_(R)). The processor 14 further calculatesa left audio channel optimal signal (Optimized signal) (O_(L))corresponded to the left audio channel error signal (E_(L)) and a rightaudio channel optimal signal (O_(R)) corresponded to the right audiochannel error signal (E_(R)).

In the real application, those optimal signals (O_(L), O_(R)) canminimize the values in the following [Equation 2]:

V=E(k)PE(k)^(T)   [Equation 2]

wherein, P is a 2×2 weighting matrix having a form of

$\quad\begin{bmatrix}1 & p_{1} \\p_{1} & 1\end{bmatrix}$

with p1<1; T is the period of over-sampling frequency.

Furthermore, the two dimensional quantitizer 16 is coupled to theprocessor 14 in order to receive left audio channel optimal signal(O_(L)) and the right audio channel optimal signal (O_(R)). Moreover,those optimal signals (O_(L), O_(R)) are converted into a second leftaudio channel triggering signal (T_(L2)) corresponded to the left audiochannel optimal signal (O_(L)) and a second right audio channeltriggering signal (T_(R2)) corresponded to the right audio channeloptimal signal (O_(R)).

Please notice that, in the current invention, the two dimensionalquantitizer 16 can transfer the second left audio channel triggeringsignal (T_(L2)) and the second right audio channel triggering signal(T_(R2)) to the second filter 12 so as to replace respectively the firstleft audio channel triggering signal (T_(L1)) and the first right audiochannel triggering signal (T_(L1)) to form a feedback circuit.

The signal generator 18 is couple to the two dimensional quantitizer 16in order to receive the second left audio channel triggering signal(T_(L2)) and the second right audio channel triggering signal (T_(R2))and generate multiple driving signals according to those secondtriggering signal (T_(L2), T_(R2)).

Finally, the logic circuit 19 contains multiple switches (not drawn inthe figure) and each switch corresponds to one of the multiple drivingsignals. Furthermore, the logic circuit 19 is coupled to the signalgenerator 18 so as to receive the multiple driving signals and controlthe corresponding switch of the logic circuit 19 according to themultiple driving signals and further drive the tri-wired stereoamplifier 30.

Please further refer to FIG. 2 which shows an embodiment of the presentinvention, that is, a logic circuit. As shown in FIG. 2, the logiccircuit 18 is a three phase full bridge circuit and contains sixswitches (S₁, S₂, S₃, S₄, S₅ and S₆). In other words, in the currentembodiment, the signal generator of the present invention (not drawn inthe figure) will generate six driving signals to control those sixswitches. Through the control on the six switches of the logic circuit18, the second left audio channel triggering signal (T_(L2)) and thesecond right audio channel triggering signal (T_(R2)) processed by classD amplifier can be transferred respectively to the left side speaker 301and the right side speaker 302 of the tri-wired stereo amplifier 30 tooutput the sound.

Please notice that, since the logic circuit 18 contains 6 switches, itthus contains 2⁶=64 kinds of switching states and only 19 states cantransfer those triggering signals to the speaker. Please see thefollowing table 1 for those 19 states.

TABLE 1 Left Right No. speaker speaker S₁ S₂ S₃ S₄ S₅ S₆ 1 P 0 On OffOff On Off Off 2 P 0L On Off Off On Off On 3 0 P Off Off Off On On Off 40L P Off On Off On On Off 5 N 0 Off On On Off Off Off 6 N 0H Off On OnOff On Off 7 0 N Off Off On Off Off On 8 0H N On Off On Off Off On 9 0H0H On Off On Off On Off 10 0H 0 On Off On Off Off Off 11 0 0H Off Off OnOff On Off 12 0L 0L Off On Off On Off On 13 0L 0 Off On Off On Off Off14 0 0L Off Off Off On Off On 15 0 0 Off Off Off Off Off Off 16 P/2 N/2On Off Off Off Off On 17 N/2 P/2 Off On Off Off On Off 18 0H/2 0H/2 OnOff Off Off On Off 19 0L/2 0L/2 Off On Off Off Off On P: positivedirection current; N: negative direction current; 0: Floatingconnections on two ends of the speaker; 0L: Two ends of the speaker andthe lower arm of full bridge are connected into a loop; 0H: Two ends ofthe speaker and the upper arm of full bridge are connected into a loop;P/2: Positive direction current with current value reduced to half; N/2:Negative direction current with current value reduced to half.

Take an example, we know from table 1 that, the states of number 1, 2, 5and 6 are to let right audio channel to stay inactive but only drive theleft audio channel. The states of number 16 and 17 drive in the sametime two audio channels with reverse current. More specifically, in thepresent embodiment, since the full bridge circuit which drives two audiochannels co-use S₃ and S₄ switches, the switching states of two audiochannels are not in independent operation to each other.

Furthermore, in one embodiment, the second left audio channel triggeringsignal (T_(L2)) and the second right audio channel triggering signal(T_(R2)) are limited to five values of 0, 1, −1, ½ and −½. Moreover, thesignal generator can generate driving signals for driving the abovementioned logic circuit according to those triggering signals. Pleaserefer to table 2 which lists the values of those triggering signals tobe corresponded to the states in table 1.

TABLE 2 T_(L) T_(R) Status No. of Table 1 1 0 1, 2 0 1 3, 4 −1   0 5, 60 −1   7, 8 0 0 9~15, 18, 19   ½ −1/2 16 −1/2   ½ 17

Yet in another embodiment, the second left audio channel triggeringsignal (T_(L2)) and the second right audio channel triggering signal(T_(R2)) can be further limited to three values of 0, 1 and −1.

Please further refer to FIG. 3A and FIG. 3B, FIG. 3A illustrates anoutput and input relationship chart of two dimensional quantitizergenerated when those above mentioned second triggering signals (T_(L2),T_(R2)) are limited to a set A={0, 1, −1, ½, −½}; FIG. 3B illustrates anoutput and input relationship chart of two dimensional quantitizergenerated when those above mentioned second triggering signals (T_(L2),T_(R2)) are limited to a set B={0, 1, −1}.

Please refer to FIG. 4 which illustrate a circuit block diagram of twodimensional quantitizer of an embodiment of the current invention; wesee that it can realize the triggering signal set of FIG. 3B. Pleasenotice that, the circuit layout of the present invention which canrealize the above mentioned triggering signal is not limited to anyspecific circuit layout, it can be other layout which is decided by thereal situation.

Please refer to FIG. 5 which illustrates a block diagram of a method fordriving a tri-wired stereo amplifier according to an embodiment of thepresent invention. As shown in FIG. 5, the method includes the followingsteps:

S51, receiving a first left audio channel sound signal (AS_(L)) and afirst right audio channel sound signal (AS_(R)).

S53, associating with an over-sampling frequency to process the firstleft audio channel sound signal (AS_(L)) to a second left audio channelsound signal (AS_(L)′) and process the first right audio channel soundsignal (AS_(R)) to a second right audio channel sound signal (AS_(R)′).

S55, re-configuring those second audio channel sound signals (A_(SL)′,AS_(R)′), a first left audio channel triggering signal (T_(L1)) and afirst right audio channel triggering signal (T_(L2)) according to afrequency weighting function so as to generate a left audio channelerror signal (E_(L)) corresponded to the second left audio channel soundsignal (AS_(L)′) and the first left audio channel triggering signal(T_(L1)) and a right audio channel error signal (E_(R)) corresponded tothe second right audio channel sound signal (AS_(R)′) and the firstright audio channel triggering signal (T_(R1)).

S57, calculating a left audio channel optimal signal (O_(L))corresponded to the left audio channel error signal (E_(L)) and a rightaudio channel optimal signal (O_(R)) corresponded to the right audiochannel error signal (E_(R)).

S59, converting those optimal signals (O_(L), O_(R)) into a second leftaudio channel triggering signal (T_(L2)) corresponded to the left audiochannel optimal signal (O_(L)) and a second right audio channeltriggering signal (T_(R2)) corresponded to the right audio channeloptimal signal (O_(R)).

S61, using respectively the second left audio channel triggering signal(TL₂) and the second right audio channel triggering signal (T_(R2)) toreplace the first left audio channel triggering signal (TL 1) and thefirst right audio channel triggering signal (T_(R1)).

S63, generating multiple driving signals according to those secondtriggering signals (T_(L2), T_(R2)).

S65, using those multiple driving signals to control the correspondingmultiple switches in a logic circuit so as to drive the tri-wired stereoamplifier.

In one embodiment, the logic circuit is a three phase full bridgecircuit. Furthermore, in real application, the three phase full bridgecircuit contains six switches and the signal generator generates sixdriving signals to control respectively the six switches.

Yet, in another embodiment, the second left audio channel triggeringsignal (T_(L2)) and the second right audio channel triggering signal(T_(R2)) are limited to five values of 0, 1, −1, ½ and −½. Further inanother embodiment, the second left audio channel triggering signal(T_(L2)) and the second right audio channel triggering signal (T_(R2))are limited to three values of 0, 1 and −1.

Furthermore, in real application, the frequency weighting function inthe method of the current invention matches the above mentioned[Equation 1]. Further in real application, those optimal signals (O_(L),O_(R)) can make the value of the above mentioned [Equation 2] thesmallest.

Obviously, class D amplifier of the present invention can be realizedthrough the above mentioned method in order to drive the tri-wiredstereo amplifier. As compared to the prior art, the class D amplifier ofthe present invention and its method can remove the need of usingcentral voltage generator circuit in the half bridge power amplifier andachieve the purpose of efficiency enhancement and cost saving. Morespecifically, since the driving signal of the present invention isgenerated through optimal feedback method of limiting conditions, themutual influence of two audio channels can thus be reduced and themismatch between two speakers can be further reduced.

Although the present invention has been disclosed as above through apreferred embodiment and the figures, it is indeed to describe but notlimit the scope of the present invention. Any one who is familiar withthe prior art can make any kinds of equivalent change and modificationwithout deviating from the spirit and scope of the present invention.Therefore, the scope of the present invention should be defined by whatis claimed.

1. A class D amplifier for driving tri-wired stereo amplifier, the classD amplifier comprising of: a first filter, receives a first left audiochannel sound signal and a first right audio channel sound signal from asound generator unit, and associates with an over-sampling frequency toprocess the first left audio channel sound signal to a second left audiochannel sound signal and process the first right audio channel soundsignal to a second right audio channel sound signal; a second filter,coupled to the first filter and a two dimensional quantitizer, is usedto receive the second left audio channel sound signal and the secondright audio channel sound signal from the first filter and to receive afirst left audio channel triggering signal and a first right audiochannel triggering signal from the two dimensional quantitizer.Moreover, a frequency weighting function is used to re-configure thosesecond audio channel sound signals and those first triggering signals soas to generate a left audio channel error signal corresponded to thesecond left audio channel sound signal and the first left audio channeltriggering signal and a right audio channel corresponded to the secondright audio channel sound signal and the first right audio channeltriggering signal; a processor, coupled to the second filter, is used toreceive the left audio channel error signal and the right audio channelerror signal. Meanwhile, those error signals are used to calculate aleft audio channel optimal signal corresponded to the left audio errorsignal and a right audio channel optimal signal corresponded to theright audio channel error signal; the two dimensional quantitizer, iscoupled to the processor, is used to receive the left audio channeloptimal signal and the right audio channel optimal signal; and convertthose optimal signals into a second left audio channel triggering signalcorresponded to the left audio channel optimal signal and a second rightaudio channel triggering signal corresponded to the right audio channeloptimal signal; the two dimensional quantitizer further transfer thesecond left audio channel triggering signal and the second right audiochannel triggering signal to the second filter so as to replacerespectively the first left audio channel triggering signal and thefirst right audio channel triggering signal; a signal generator, coupledto the two dimensional quantitizer, is used to receive the second leftaudio channel triggering signal and the second right audio channeltriggering signal and generate multiple driving signals according tothose second triggering signals; and a logic circuit, comprising ofmultiple switches, wherein each switch is corresponded to one of themultiple driving signals and the logic circuit is coupled to the signalgenerator to receive the multiple driving signals and the correspondingswitch in the logic circuit is controlled according to the multipledriving signals in order to drive the tri-wired stereo amplifier.
 2. Theclass D amplifier claimed in claim 1, wherein the logic circuit is athree phase full bridge circuit.
 3. The class D amplifier claimed inclaim 2, wherein the three phase full bridge circuit contains sixswitches and the signal generator generates six driving signals to driverespectively the six switches.
 4. The class D amplifier claimed in claim1, wherein the second left audio channel triggering signal and thesecond right audio channel triggering signal are all selected from a setformed by five values of 0, 1, −1, ½ and −½.
 5. The class D amplifierclaimed in claim 4, wherein the second left audio channel triggeringsignal and the second right audio channel triggering signal are allselected from a set formed by three values of 0, 1 and −1.
 6. The classD amplifier claimed in claim 1, wherein the frequency weighting averagematches the following equation: $\left\{ {\begin{matrix}{\begin{bmatrix}{X_{R}\left( {k + 1} \right)} \\{X_{L}\left( {k + 1} \right)}\end{bmatrix} = {{A\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {B\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}} \\{\begin{bmatrix}{E_{R}(k)} \\{E_{L}(k)}\end{bmatrix} = {{C\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {D\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}}\end{matrix};} \right.$ wherein, $\begin{bmatrix}X_{R} \\X_{L}\end{bmatrix} \in R^{n \times 1}$ is the state of the CLASS D AMPLIFIER;AεR^(n×n); BεR^(n×2); CεR^(2×n); and DεR^(2×2).
 7. The class D amplifierclaimed in claim 1, wherein those optimal signals (O_(L), O_(R)) canmake the value of the following equation the smallest:V=E(k)PE(k)^(T); wherein, P is 2×2 weighting matrix having a form of$\begin{bmatrix}1 & p_{1} \\p_{1} & 1\end{bmatrix},$ and p1<1; T is the period of the over-samplingfrequency.
 8. A method for driving tri-wired stereo amplifier,comprising of the following steps: (a) Receiving a first left audiochannel sound signal and a first right audio channel sound signal; (b)Associating with an over-sampling frequency to process the first leftaudio channel sound signal to a second left audio channel sound signaland to process the first right audio channel sound signal to a secondright audio channel sound signal; (c) Re-configuring those second audiochannel sound signal, a first left audio channel triggering signal and afirst right audio channel triggering signal according to frequencyweighting function so as to generate a left audio channel error signalcorresponded to the second left audio channel sound signal and the firstleft audio channel triggering signal and a right audio channel errorsignal corresponded to the second right audio channel sound signal andthe first right audio channel triggering signal; (d) Calculating,according to those error signals, a left audio channel optimal signalcorresponded to the left audio channel error signal and a right audiochannel optimal signal corresponded to the right audio channel errorsignal; (e) Converting those optimal signals into a second left audiochannel triggering signal corresponded to the left audio channel optimalsignal and a second right audio channel triggering signal correspondedto the right audio channel optimal signal; (f) Using respectively thesecond left audio channel triggering signal and the second right audiochannel triggering signal to replace the first left audio channeltriggering signal and the first right audio channel triggering signal;(g) Generating multiple driving signals according to those secondtriggering signal; and (h) Controlling the corresponding multipleswitches of logic circuit according to the multiple driving signals soas to drive the tri-wired stereo amplifier.
 9. The method claimed inclaim 8, wherein the logic circuit is a three phase full bridge circuit.10. The method claimed in claim 9, wherein the three phase full bridgecircuit contains six switches and the signal generator generates sixdriving signals to control respectively the six switches.
 11. The methodclaimed in claim 8, wherein the second left audio channel triggeringsignal and the second right audio channel triggering signal are allselected from one of the value in the set formed by the five values of0, 1, −1, ½ and −½.
 12. The method claimed in claim 11, wherein thesecond left audio channel triggering signal and the second right audiochannel triggering signal are all selected from one of the value in theset formed by the three values of 0, 1 and −1.
 13. The method claimed inclaim 8, wherein the frequency weighting function matches the followingequation: $\left\{ {\begin{matrix}{\begin{bmatrix}{X_{R}\left( {k + 1} \right)} \\{X_{L}\left( {k + 1} \right)}\end{bmatrix} = {{A\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {B\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}} \\{\begin{bmatrix}{E_{R}(k)} \\{E_{L}(k)}\end{bmatrix} = {{C\begin{bmatrix}{X_{R}(k)} \\{X_{L}(k)}\end{bmatrix}} + {D\begin{bmatrix}{{{AS}_{R}^{\prime}(k)} - {T_{R\; 1}(k)}} \\{{{AS}_{L}^{\prime}(k)} - {T_{L\; 1}(k)}}\end{bmatrix}}}}\end{matrix};} \right.$ Wherein, $\begin{bmatrix}X_{R} \\X_{L}\end{bmatrix} \in R^{n \times 1}$ is the state of CLASS D AMPLIFIER;AεR^(n×n); BεR^(n×2); CεR^(2×n); and DεR^(2×2).
 14. The method claimedin claim 8, wherein those optimal signals (O_(L), O_(R)) can make thevalue of the following equation the smallest:V=E(k)PE(k)^(T); wherein, P is a 2×2 weighting matrix having the form of$\quad\begin{bmatrix}1 & p_{1} \\p_{1} & 1\end{bmatrix}$ and p1<1; T is the period of over-sampling frequency.